import java.util.Arrays;

public class PriorityQueue {
    public int[] elem;
    public int usedSize;

    public PriorityQueue() {
        this.elem = new int[10];
        this.usedSize = 0;
    }

    /**
     * 建堆的时间复杂度：
     *
     * @param array
     */
    public void createHeap(int[] array) {
        if(this.elem.length < array.length) Arrays.copyOf(this.elem, array.length);
        for(int i = 0; i < array.length; i++)
        {
            this.elem[i] = array[i];
            usedSize++;
        }


        for(int parent = (usedSize - 1 - 1) / 2; parent >= 0; parent--)
        {
            shiftDown(parent, usedSize);
        }
    }

    /**
     *
     * @param root 是每棵子树的根节点的下标
     * @param len  是每棵子树调整结束的结束条件
     * 向下调整的时间复杂度：O(logn)
     */
    private void shiftDown(int root,int len) {
        int parent = root;
        int child = root * 2 + 1;
        while (child < len)
        {
            if(child + 1 < len && this.elem[child] < this.elem[child + 1])
            {
                child = child + 1;
            }
            if(this.elem[child] > this.elem[parent])
            {
                sawp(child, parent);
                parent = child;
                child = parent * 2 + 1;
            }
            else
            {
                break;
            }
        }
    }

    private void sawp(int i, int j) {
        int tmp = this.elem[i];
        this.elem[i] = this.elem[j];
        this.elem[j] = tmp;
    }


    /**
     * 入队：仍然要保持是大根堆
     * @param val
     */
    public void push(int val) {
        if(isFull()) Arrays.copyOf(this.elem, this.elem.length * 2);
        this.elem[usedSize] = val;
        shiftUp(usedSize);
        usedSize++;
    }

    private void shiftUp(int child) {
        int parent = (child - 1) / 2;
        while(child > 0)
        {
            if(this.elem[child] > this.elem[parent])
            {
                sawp(child, parent);
                child = parent;
                parent = (child - 1) / 2;
            }
            else
            {
                break;
            }
        }
    }

    public boolean isFull() {
        return this.elem.length == this.usedSize;
    }

    /**
     * 出队【删除】：每次删除的都是优先级高的元素
     * 仍然要保持是大根堆
     */
    public void pollHeap() {
        if(isEmpty()) return ;
        sawp(0, usedSize - 1);
        usedSize--;
        shiftDown(0,usedSize);
    }

    public boolean isEmpty() {
        return this.usedSize == 0;
    }

    /**
     * 获取堆顶元素
     * @return
     */
    public int peekHeap() {
        if(isEmpty()) return -1;
        return this.elem[0];
    }
}